"Pertussis (whooping cough) can cause serious illness in babies, children, teens, and adults. Symptoms of pertussis usually develop within 5 to 10 days after being exposed, but sometimes not for as long as 3 weeks.

The disease usually starts with cold-like symptoms and maybe a mild cough or fever. In babies, the cough can be minimal or not even there. Babies may have a symptom known as "apnea." Apnea is a pause in the child's breathing pattern. Pertussis is most dangerous for babies. About half of babies younger than 1 year who get the disease need care in the hospital. Learn more about pertussis complications.

Early symptoms can last for 1 to 2 weeks and usually include:

Runny nose

Low-grade fever (generally minimal throughout the course of the disease)

Mild, occasional cough

Apnea – a pause in breathing (in babies)

Because pertussis in its early stages appears to be nothing more than the common cold, it is often not suspected or diagnosed until the more severe symptoms appear."